The present invention relates to a fresh-air intake duct for a motor vehicle with an inlet grill retaining any coarse impurities and at least one drainage aperture, located in the area of the lowest point of the fresh-air intake duct, for liquid separated out from the air current.
A fresh-air intake duct, with which, even before the inlet grill, drops of liquid separate out in a gutter and with which a residual liquid separate out in a gutter and with which a residual liquid separation is brought about by deflection of the air current, is shown in DE-PS 33 30 951. This liquid separation works with a high degree of efficiency, yet requires, a large amount of construction space and a specified air channel, particularly because of the air deflection. With fresh-air intake ducts orientated in the cross-vehicle direction, such space is not generally available.
An object of the present invention is to provide liquid separation which works with a high degree of efficiency within a fresh-air intake duct without any air deflection and which is thus suitable for use in intake ducts which essentially extend in a straight line.
This object has been achieved, in the case of a fresh-air duct according to the present invention by mounting air-permeable and water-permeable baffles in the form of a fine-meshed grill in front of the upwardly projecting side walls of the fresh air intake duct, and the liquid making its way through the meshes of the grill, in the flow vacuum between a baffles and a side wall at the back of the baffle, to flow away downwards to the duct bottom and to the drainage aperture. The liquid settling at the side is this no longer as before, i.e. in the absence of an air-permeable or water-permeable baffle mounted in front, carried along by the wall current in the direction of flow and, upon becoming detached, finely re-scattered. Instead, the liquid accumulating at the back of the baffle is able due to the absence of a directed current, to flow away by gravitational pull downwards to the duct bottom.
A periodically constant distance between the baffle and the duct wall without the use of spacers is achieved if the grill is provided with uniformly continuous-running waves, the wave troughs of which come into contact with the associated side wall of the fresh-air intake duct. Consequently, a flow vacuum is created between two respective wave troughs, in which flow vacuum, on the grill side, liquid is able to flow away downwardly.
In a currently preferred embodiment of the present invention, the wave, viewed in the flow direction of the air, run downwards at an angle of approximately 45.degree., which is beneficial to the drainage behavior. The wave height advantageously measures approximately 4 mm and the material thickness, in order to obtain good adaptability to variously inclined or variously crooked-running side-wall section, measures approximately 0.3 mm. A mesh width of approximately 1 mm has proved to be particularly effective.